Wall structures formed from a plurality of interconnected, prefabricated and portable panels are used extensively in commercial and industrial buildings for dividing interior regions into smaller work regions. Such structures have proven particularly effective in providing greater privacy within the building, and at the same time improving the interior appearance. For this purpose, the panels are provided with many different exterior finishes, such as colored plastics, carpets and fabrics. Some of these panels also tend to minimize noise, particularly when they are provided with soft exterior finishes, such as by being covered with carpeting or fabric. Many panels of this type are also provided with slotted rails extending vertically along the edges thereof, whereupon fixtures such as desks, shelves, filing cabinets and the like can be mounted on the panels. Due to the desire to mount these fixtures on the panels, the panels thus must be provided with substantial strength and, accordingly, are normally provided with a relatively strong and rigid core so as to provide the necessary strength.
While panels of the above type do tend to minimize noise, nevertheless any noise absorption capability of the panel is normally provided solely by the outer coverings. Further, since these panels are normally of a height substantially less than the floor-to-ceiling height, this also permits the transmission of substantial noise over the panel which, when coupled with the inability of these panels to absorb a high percentage of sound at various frequencies, thus results in these panels being unacceptable for use in situations where a high noise reduction and absorption by the panel is necessary. Because of this inability to absorb a high percentage of the sound in the environment, these known panels have conventionally been referred to as non-acoustical-type panels.
In recognition of this problem, copending applications Ser. No. 631,855, filed Nov. 14, 1975, now Pat. No. 4,084,366, and Ser. No. 761,777, filed Jan. 24, 1977, now Pat. No. 4,084,367, which are both owned by the assignee of this invention, disclose an acoustical panel which represents a substantial improvement over prior structures in terms of its ability to absorb a high percentage of various frequency sound waves while at the same time being both aesthetically pleasing in appearance and structurally strong so as to permit accessories and fixtures to be hung thereon. In the panel disclosed in the above-mentioned applications, the core of the panel is provided with a honeycomb structure which is covered by perforated side skins to form a plurality of Helmholtz resonators for effectively absorbing sound waves, particularly those sound waves of lower frequencies. The side skins in turn are covered by layers of porous sound absorbing material, such as fiber glass, to effectively absorb those sound waves of high frequencies, whereby the resultant panel possesses a capability of absorbing a high percentage of the sound wave frequencies normally encountered within an office-type working environment, with the resultant panel thus having a high noise reduction coefficient (NRC).
While the panel disclosed in the above-mentioned applications has proven extremely successful for absorbing the undesired sound frequencies while still possessing the necessary structural strength required for hanging fixtures and the like, nevertheless substantial additional research and development has been carried out on acoustical panels of this type in an attempt to further improve upon the structural and sound absorbing characteristics thereof, particularly so as to provide an improved panel which can be manufactured and assembled in a more economical manner while at the same time retaining or improving upon the desired sound absorption characteristics of the panel. For example, in a preferred embodiment of the panel disclosed in the above-mentioned applications, two honeycomb layers are disposed back-to-back within the core, and each layer has cells of at least two different sizes. This structure is costly in view of the need to use specialized honeycomb possessing several sizes of cells, and the necessity of having to utilize two honeycomb layers within each panel. This additionally increases the complexity of the manufacturing and assembling techniques, and complicates the necessary alignment between the apertures in the side skins and the cells of the honeycomb layers in order to provide the desired Helmholtz sound-absorbing resonators.
Accordingly, it is an object of the present invention to provide an improved acoustical panel for absorbing a large degree of directed sound of various frequencies, which panel possesses a high noise reduction coefficient and also possesses substantial strength to enable fixtures to be hung thereon, and which can be manufactured in a simplified and more economical manner.
It is also an object of this invention to provide an improved acoustical panel, as aforesaid, which can utilize a standardized honeycomb layer of a single cell size, which can utilize a single honeycomb layer within the panel core, and which has pluralities of honeycomb cells communicating with apertures in the opposite side skins of the panel to form Helmholtz resonators on both sides of the panel.
Another object of the invention is to provide an acoustical panel, as aforesaid, wherein identical side skins can be provided on opposite sides of the panel, which skins have a selected pattern of apertures therein so that a single honeycomb layer can be utilized within the core while a first plurality of cells communicate with one side of the panel and a second plurality of cells communicate with the other side of the panel, thereby forming Helmholtz resonators communicating with both sides of the panel, while at the same time resulting in a simplified panel structure which is economical to manufacture and assemble.
A further object of this invention is to provide an improved acoustical panel, as aforesaid, which permits efficient absorption of an even larger range of sound wave frequencies by permitting the formation of a large number of different Helmholtz resonators capable of absorbing different sound wave frequencies, while at the same time providing a panel which is of maximum structural simplicity and which permits manufacturing and assembling of the panel in a manner which maximizes the permissible manufacturing and assembly tolerances while still resulting in a panel possessing the desired Helmholtz resonators.
Other objects and purposes of the invention will be apparent to persons familiar with structures of this general type upon reading the following specification and inspecting the accompanying drawings.